US5654678A - Level-controlled oscillation circuit having a continuously variable impedance control circuit - Google Patents

Level-controlled oscillation circuit having a continuously variable impedance control circuit Download PDF

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US5654678A
US5654678A US08/610,517 US61051796A US5654678A US 5654678 A US5654678 A US 5654678A US 61051796 A US61051796 A US 61051796A US 5654678 A US5654678 A US 5654678A
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Prior art keywords
circuit
oscillation
continuously variable
level
variable impedance
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US08/610,517
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Shinichi Miyazaki
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NEC Corp
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NEC Corp
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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
    • H03B5/00—Generation of oscillations using amplifier with regenerative feedback from output to input
    • H03B5/30—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element being electromechanical resonator
    • H03B5/32—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element being electromechanical resonator being a piezoelectric resonator
    • H03B5/36—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element being electromechanical resonator being a piezoelectric resonator active element in amplifier being semiconductor device
    • H03B5/366—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element being electromechanical resonator being a piezoelectric resonator active element in amplifier being semiconductor device and comprising means for varying the frequency by a variable voltage or current
    • H03B5/368—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element being electromechanical resonator being a piezoelectric resonator active element in amplifier being semiconductor device and comprising means for varying the frequency by a variable voltage or current the means being voltage variable capacitance diodes
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
    • H03B2200/00—Indexing scheme relating to details of oscillators covered by H03B
    • H03B2200/0002—Types of oscillators
    • H03B2200/0008—Colpitts oscillator
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
    • H03B2200/00—Indexing scheme relating to details of oscillators covered by H03B
    • H03B2200/003—Circuit elements of oscillators
    • H03B2200/004—Circuit elements of oscillators including a variable capacitance, e.g. a varicap, a varactor or a variable capacitance of a diode or transistor
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
    • H03B2200/00—Indexing scheme relating to details of oscillators covered by H03B
    • H03B2200/006—Functional aspects of oscillators
    • H03B2200/0066—Amplitude or AM detection
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
    • H03B2201/00—Aspects of oscillators relating to varying the frequency of the oscillations
    • H03B2201/02—Varying the frequency of the oscillations by electronic means
    • H03B2201/0208—Varying the frequency of the oscillations by electronic means the means being an element with a variable capacitance, e.g. capacitance diode

Definitions

  • the present invention relates to an oscillation circuit applicable to various kinds of electronic apparatuses as a clock source and, more particularly, to an oscillation circuit of the type using a quartz oscillator and free from the accidental fall of oscillation level and the accidental stop of oscillation.
  • a conventional oscillation circuit particularly one using a quartz oscillator, oscillates continuously only when the resistance Rx of the oscillator relative to the frequency and the negative resistance --Ro of the circuit satisfy a relation
  • the oscillation is stabilized when the oscillation level increases until
  • the problem with the conventional circuit is that when the negative resistance --Ro of the circuit decreases due to, for example, a change in ambient temperature, the oscillation level also fails. Further, when the negative resistance --Ro of the circuit decreases to below the resistance Rx of the oscillator, the circuit practically stops oscillating.
  • an object of the present invention to provide an oscillation circuit which does not fall in oscillation level or does not stop oscillating without regard to temperature and other ambient conditions.
  • An oscillation circuit of the present invention comprises a resonance circuit including a quartz oscillator, an active circuit for driving the quartz oscillator, a variable impedance circuit connected to the resonance circuit for changing the reactance of the quartz oscillator, a detecting circuit for detecting the output level of the active circuit, and an impedance control circuit for controlling the variable impedance circuit in response to an output level detected by the detecting circuit.
  • FIG. 1 is a circuit diagram showing a conventional oscillation circuit
  • FIG. 2 shows an equivalent circuit representative of a quartz oscillator and capacitors included in the conventional circuit
  • FIG. 3A is a graph indicating the impedance characteristic of the quartz oscillator
  • FIG. 3B is a graph showing the impedance characteristic of the conventional oscillation circuit
  • FIG. 3C is a graph representative of a relation between the oscillation level and the negative resistance
  • FIG. 4 is a graph indicative of changes in negative resistance
  • FIG. 5 is a circuit diagram representative of an oscillation circuit embodying the present invention.
  • FIG: 6 is a graph indicative of a characteristic particular to a varactor diode included in the embodiment.
  • the oscillation circuit has a quartz oscillator X 1 , a transistor Tr 1 , resistors R 1 , R 2 and R 3 , capacitors C 1 , C 2 and C 3 , and an output terminal OUT.
  • the resistor R 1 sets the operation current of the circuit while the resistors R 2 and R 3 set the bias voltage of the transistor Tr 1 .
  • the capacitor C 3 is used to connect the collector of the transistor Tr 1 to to ground.
  • the capacitors C 1 and C 2 and quartz oscillator X 1 constitute in combination a feedback section, as represented by an equivalent circuit in FIG. 2.
  • the prerequisite with the oscillation circuit is that the oscillator X 1 be provided with an inductive reactance characteristic, i.e., oscillatory at a frequency exhibiting an inductive reactance characteristic.
  • FIGS. 3A-3C the impedance characteristic of the oscillator X 1 and that of the oscillation circuit will be described.
  • the impedance characteristics are each measured at a point A shown in FIG. 1.
  • FIG. 3A indicates the impedance characteristic of the oscillator X 1 .
  • the resistance Rx of the oicillator X 1 tends to increase as the frequency exceeds a resonance frequency Po.
  • the impedance characteristic of the oscillation circuit (negative resistance --Ro and reactance Xc) is determined by the transistor Tr 1 and capacitors C 1 and C 2 ; generally, the impedance changes little relative the frequency.
  • FIG. 3C indicates a relation between the oscillation level Po of the oscillation circuit and the negative resistance --Ro. As shown, the negative resistance --Ro tends to decrease with the increase in oscillation level Po.
  • the precondition for the conventional oscillation circuit to oscillate is as follows. Oscillation begins at a frequency at which the absolute value of both the capacitive reactance Xc of the oscillation circuit and the inductive reactance Xe of the quartz oscillator X 1 coincide (point B, FIG. 3A). When the resistance Rx of the oscillator X 1 as measured at the above-mentioned frequency is smaller than the absolute value of the negative resistance --Ro of the circuit, the oscillation continues. As the oscillation level increases to one at which
  • the conventional oscillation circuit has a drawback that, as shown in FIG. 4, the oscillation level fails when the negative resistance of the circuit decreases due to, for example, a change in ambient temperature. Moreover, the circuit practically stops oscillating when the negative resistance thereof decreases to below the resistance of the quartz oscillator X 1 .
  • the oscillation circuit has a resonance circuit 10 including a quartz oscillator X 1 , an active circuit 12 for driving the oscillator X 1 and having an output terminal OUT, a variable impedance circuit 14 connected to the resonance circuit 10, an output level detecting circuit 16 connected to the output terminal OUT, and an impedance control circuit 18 for controlling the variable impedance circuit 14 in response to a level detected by the detecting circuit 16. Specifically, when the output level falls as detected by the detecting circuit 16, the impedance control circuit 18 so controls the variable impedance circuit 14 as to lower the equivalent resistance of the oscillator X 1 .
  • the impedance circuit 14 is implemented by a varactor diode connected in series with the oscillator X 1 , as will be described in detail later.
  • a transistor Tr 1 , capacitors C 1 -C 3 and resistors R 1 -R 3 also shown in FIG. 5 will not be described specifically since they are identical with the corresponding constituents of the conventional circuit.
  • the impedance circuit 14 for causing the reactance X1 of the oscillator X 1 to change is made up of a varactor diode V 1 and a resistor R 7 which feeds a bias voltage.
  • the varactor diode V 1 has a capacitive reactance Xv. As shown in FIG. 6, the capacitive reactance Xv of the diode V 1 increases with the increase in bias voltage. In this sense, the varactor diode V 1 and oscillator X 1 cooperate as a resonance circuit for changing the impedance.
  • the detecting circuit I6 responsive to the output level of the oscillation circuit is made up of a loose coupling capacitor C4, and a capacitor C5, a diode V2, and a resistor R4 which constitute a conventional high frequency detector in combination.
  • the oscillation output signal is loosely coupled by the capacitor C4 and then detected by the detector, i.e., diode V2, resistor R4 and capacitor C5.
  • the signal detected by such a detector is a DC voltage; the voltage is high when the output level is high or low when the output level is low.
  • the resulting output of the detecting circuit 16 is applied to an operational amplifier OP1 included in the impedance control circuit 18.
  • the impedance control circuit 18 is implemented as a conventional in-phase amplifier having the operational amplifier OP1 and resistors R5 and R6.
  • the control circuit 18 processes the output of the detecting circuit 16 and then delivers the result of processing to the varactor diode V1 via the resistor R7.
  • the negative resistance --Ro of the oscillation circuit has decreased due to, for example, a change in ambient temperature, causing the output level of the circuit to fall. Then, the bias voltage of the varactor diode V1 and, therefore, the capacitive reactance Xv of the diode V1 is lowered. As a result, the inductive reactance XI of the oscillator X 1 increases to in turn lower the oscillation frequency. This is because the impedance of the oscillation circuit is constant. Further, since the resistance of the resonance circuit 10, i.e., the resistance of the oscillator X 1 decreases with the decrease in frequency, the oscillation level is prevented from falling despite the fall of the negative resistance --Ro of the oscillation circuit.
  • the present invention provides an oscillation circuit whose oscillation does not fall in level or does not stop without regard to ambient conditions, e.g., temperature.

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  • Oscillators With Electromechanical Resonators (AREA)
  • Inductance-Capacitance Distribution Constants And Capacitance-Resistance Oscillators (AREA)

Abstract

An oscillation circuit using a quartz oscillator. When the output level of the oscillation circuit falls, this output level change is detected and the reactance of the quartz oscillator is changed such that the circuit oscillates at a frequency which reduces the resistance of the oscillator. Hence, the oscillation of the circuit does not fall in level or stop regardless of temperature and other ambient conditions.

Description

This application is a continuation of application Ser. No. 08/161,547, filed Dec. 6, 1993, now abandoned.
BACKGROUND OF THE INVENTION
The present invention relates to an oscillation circuit applicable to various kinds of electronic apparatuses as a clock source and, more particularly, to an oscillation circuit of the type using a quartz oscillator and free from the accidental fall of oscillation level and the accidental stop of oscillation.
A conventional oscillation circuit, particularly one using a quartz oscillator, oscillates continuously only when the resistance Rx of the oscillator relative to the frequency and the negative resistance --Ro of the circuit satisfy a relation |-Ro|>|Rx|. The oscillation is stabilized when the oscillation level increases until |Rx|=|--Ro| holds.
However, the problem with the conventional circuit is that when the negative resistance --Ro of the circuit decreases due to, for example, a change in ambient temperature, the oscillation level also fails. Further, when the negative resistance --Ro of the circuit decreases to below the resistance Rx of the oscillator, the circuit practically stops oscillating.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide an oscillation circuit which does not fall in oscillation level or does not stop oscillating without regard to temperature and other ambient conditions.
An oscillation circuit of the present invention comprises a resonance circuit including a quartz oscillator, an active circuit for driving the quartz oscillator, a variable impedance circuit connected to the resonance circuit for changing the reactance of the quartz oscillator, a detecting circuit for detecting the output level of the active circuit, and an impedance control circuit for controlling the variable impedance circuit in response to an output level detected by the detecting circuit.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description taken with the accompanying drawings in which:
FIG. 1 is a circuit diagram showing a conventional oscillation circuit;
FIG. 2 shows an equivalent circuit representative of a quartz oscillator and capacitors included in the conventional circuit;
FIG. 3A is a graph indicating the impedance characteristic of the quartz oscillator;
FIG. 3B is a graph showing the impedance characteristic of the conventional oscillation circuit;
FIG. 3C is a graph representative of a relation between the oscillation level and the negative resistance;
FIG. 4 is a graph indicative of changes in negative resistance;
FIG. 5 is a circuit diagram representative of an oscillation circuit embodying the present invention; and
FIG: 6 is a graph indicative of a characteristic particular to a varactor diode included in the embodiment.
DESCRIPTION OF THE PREFERRED EMBODIMENT
To better understand the present invention, a brief reference will be made to a conventional oscillation circuit, shown in FIG. 1. As shown, the oscillation circuit has a quartz oscillator X1, a transistor Tr1, resistors R1, R2 and R3, capacitors C1, C2 and C3, and an output terminal OUT. The resistor R1 sets the operation current of the circuit while the resistors R2 and R3 set the bias voltage of the transistor Tr1. The capacitor C3 is used to connect the collector of the transistor Tr1 to to ground. The capacitors C1 and C2 and quartz oscillator X1 constitute in combination a feedback section, as represented by an equivalent circuit in FIG. 2. The prerequisite with the oscillation circuit is that the oscillator X1 be provided with an inductive reactance characteristic, i.e., oscillatory at a frequency exhibiting an inductive reactance characteristic.
Referring to FIGS. 3A-3C, the impedance characteristic of the oscillator X1 and that of the oscillation circuit will be described. The impedance characteristics are each measured at a point A shown in FIG. 1. Specifically, FIG. 3A indicates the impedance characteristic of the oscillator X1. As shown, the resistance Rx of the oicillator X1 tends to increase as the frequency exceeds a resonance frequency Po. On the other hand, as shown in FIG. 3B, the impedance characteristic of the oscillation circuit (negative resistance --Ro and reactance Xc) is determined by the transistor Tr1 and capacitors C1 and C2 ; generally, the impedance changes little relative the frequency. FIG. 3C indicates a relation between the oscillation level Po of the oscillation circuit and the negative resistance --Ro. As shown, the negative resistance --Ro tends to decrease with the increase in oscillation level Po.
The precondition for the conventional oscillation circuit to oscillate is as follows. Oscillation begins at a frequency at which the absolute value of both the capacitive reactance Xc of the oscillation circuit and the inductive reactance Xe of the quartz oscillator X1 coincide (point B, FIG. 3A). When the resistance Rx of the oscillator X1 as measured at the above-mentioned frequency is smaller than the absolute value of the negative resistance --Ro of the circuit, the oscillation continues. As the oscillation level increases to one at which |Rx|=|--Ro| holds, the oscillation is stabilized.
However, the conventional oscillation circuit has a drawback that, as shown in FIG. 4, the oscillation level fails when the negative resistance of the circuit decreases due to, for example, a change in ambient temperature. Moreover, the circuit practically stops oscillating when the negative resistance thereof decreases to below the resistance of the quartz oscillator X1.
Referring to FIG. 5, an oscillation circuit embodying the present invention is shown. As shown, the oscillation circuit has a resonance circuit 10 including a quartz oscillator X1, an active circuit 12 for driving the oscillator X1 and having an output terminal OUT, a variable impedance circuit 14 connected to the resonance circuit 10, an output level detecting circuit 16 connected to the output terminal OUT, and an impedance control circuit 18 for controlling the variable impedance circuit 14 in response to a level detected by the detecting circuit 16. Specifically, when the output level falls as detected by the detecting circuit 16, the impedance control circuit 18 so controls the variable impedance circuit 14 as to lower the equivalent resistance of the oscillator X1. The impedance circuit 14 is implemented by a varactor diode connected in series with the oscillator X1, as will be described in detail later. A transistor Tr1, capacitors C1 -C3 and resistors R1 -R3 also shown in FIG. 5 will not be described specifically since they are identical with the corresponding constituents of the conventional circuit.
The impedance circuit 14 for causing the reactance X1 of the oscillator X1 to change is made up of a varactor diode V1 and a resistor R7 which feeds a bias voltage. The varactor diode V1 has a capacitive reactance Xv. As shown in FIG. 6, the capacitive reactance Xv of the diode V1 increases with the increase in bias voltage. In this sense, the varactor diode V1 and oscillator X1 cooperate as a resonance circuit for changing the impedance.
The detecting circuit I6 responsive to the output level of the oscillation circuit is made up of a loose coupling capacitor C4, and a capacitor C5, a diode V2, and a resistor R4 which constitute a conventional high frequency detector in combination. The oscillation output signal is loosely coupled by the capacitor C4 and then detected by the detector, i.e., diode V2, resistor R4 and capacitor C5. The signal detected by such a detector is a DC voltage; the voltage is high when the output level is high or low when the output level is low.
The resulting output of the detecting circuit 16 is applied to an operational amplifier OP1 included in the impedance control circuit 18. The impedance control circuit 18 is implemented as a conventional in-phase amplifier having the operational amplifier OP1 and resistors R5 and R6. The control circuit 18 processes the output of the detecting circuit 16 and then delivers the result of processing to the varactor diode V1 via the resistor R7.
Assume that the negative resistance --Ro of the oscillation circuit has decreased due to, for example, a change in ambient temperature, causing the output level of the circuit to fall. Then, the bias voltage of the varactor diode V1 and, therefore, the capacitive reactance Xv of the diode V1 is lowered. As a result, the inductive reactance XI of the oscillator X1 increases to in turn lower the oscillation frequency. This is because the impedance of the oscillation circuit is constant. Further, since the resistance of the resonance circuit 10, i.e., the resistance of the oscillator X1 decreases with the decrease in frequency, the oscillation level is prevented from falling despite the fall of the negative resistance --Ro of the oscillation circuit.
In summary, it will be seen that the present invention provides an oscillation circuit whose oscillation does not fall in level or does not stop without regard to ambient conditions, e.g., temperature.
Various modifications will become possible for those skilled in the art after receiving the teachings of the present disclosure without departing from the scope thereof.

Claims (3)

What is claimed is:
1. A level-controlled oscillation circuit comprising:
a resonance circuit including a quartz oscillator;
an active circuit for driving said quartz oscillator;
a continuously variable impedance circuit connected to said resonance circuit for continuously varying a reactance of said quartz oscillator;
a detecting circuit for detecting an output level of said active circuit; and
an impedance control circuit for controlling said continuously variable impedance circuit in response to an output level detected by said detecting circuit;
a capacitive reactance of said continuously variable impedance circuit varying proportionally with said detected output level, said impedance control circuit, by continuously varying said capacitive reactance of said continuously variable impedance circuit, controls an output level of said level-controlled oscillation circuit by maintaining an impedance of said resonance circuit constant despite a fall in a negative resistance of said resonance circuit occasioned by changes in ambient conditions.
2. An oscillation circuit as claimed in claim 1, wherein said impedance control circuit controls, when the output level detected by said detecting circuit falls, said continuously variable impedance circuit such that an equivalent resistance of said quartz oscillator decreases.
3. An oscillation circuit as claimed in claim 1, wherein said continuously variable impedance circuit comprises a varactor diode connected in series with said quartz oscillator.
US08/610,517 1992-12-07 1996-03-04 Level-controlled oscillation circuit having a continuously variable impedance control circuit Expired - Fee Related US5654678A (en)

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JP4326922A JP2626432B2 (en) 1992-12-07 1992-12-07 Oscillation circuit
JP4-326922 1992-12-07
US16154793A 1993-12-06 1993-12-06
US08/610,517 US5654678A (en) 1992-12-07 1996-03-04 Level-controlled oscillation circuit having a continuously variable impedance control circuit

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JP (1) JP2626432B2 (en)
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US5894248A (en) * 1997-06-11 1999-04-13 Wiltron Company Controlled loop gain YIG tuned oscillator circuit
CN102739154A (en) * 2011-04-06 2012-10-17 上海炬力集成电路设计有限公司 Temperature coefficient correction method in system on a chip and system on a chip
US9306402B1 (en) * 2013-02-07 2016-04-05 Analog Devices, Inc. Circuits and methods for capacitor charging
JP2016103772A (en) * 2014-11-28 2016-06-02 株式会社大真空 Oscillator
US10256771B2 (en) 2016-06-10 2019-04-09 Fujitsu Limited Crystal oscillator device and method of measuring crystal oscillator characteristic
US10333480B2 (en) 2016-06-10 2019-06-25 Fujitsu Limited Crystal oscillator device and method of measuring crystal oscillator characteristic
US10340850B2 (en) 2016-06-10 2019-07-02 Fujitsu Limited Crystal oscillator device and method of measuring crystal oscillator characteristic
US10355641B2 (en) 2016-06-10 2019-07-16 Fujitsu Limited Crystal oscillator device and method of measuring crystal oscillator characteristic
US10355640B2 (en) 2016-06-10 2019-07-16 Fujitsu Limited Crystal oscillator device and method of measuring crystal oscillator characteristic
US10476435B2 (en) 2016-06-10 2019-11-12 Fujitsu Limited Crystal oscillator, crystal resonator controlling method, and crystal resonator controlling device

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US5534826A (en) * 1994-10-24 1996-07-09 At&T Corp. Oscillator with increased reliability start up
DE19611610A1 (en) * 1996-03-23 1997-09-25 Philips Patentverwaltung Oszillaotr
FI101657B1 (en) * 1996-07-25 1998-07-31 Nokia Mobile Phones Ltd Voltage controlled oscillator connection
GB9807052D0 (en) * 1998-04-02 1998-06-03 Philips Consumer Communication Communications device
KR100286562B1 (en) * 1999-02-01 2001-03-15 윤종용 A brake device of washing machine
JP5205827B2 (en) * 2007-06-14 2013-06-05 日本電気株式会社 Oscillation frequency control method and oscillator

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US3560880A (en) * 1968-12-23 1971-02-02 Us Navy Crystal oscillator with automatic compensation for frequency drift due to aging
FR2305056A1 (en) * 1975-03-20 1976-10-15 Philips Nv STABILIZED OSCILLATORS
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JPS61278201A (en) * 1985-06-03 1986-12-09 Kinseki Kk Crystal oscillator with digital temperature compensation
US4851791A (en) * 1987-09-29 1989-07-25 Compagnie D'electronique Et De Piezoelectricite - C.E.P.E. Temperature-compensated piezoelectric oscillator
US5101178A (en) * 1990-03-27 1992-03-31 Nec Corporation Crystal oscillator having frequency adjustment responsive to power supply voltage

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5894248A (en) * 1997-06-11 1999-04-13 Wiltron Company Controlled loop gain YIG tuned oscillator circuit
CN102739154A (en) * 2011-04-06 2012-10-17 上海炬力集成电路设计有限公司 Temperature coefficient correction method in system on a chip and system on a chip
CN102739154B (en) * 2011-04-06 2015-09-23 上海炬力集成电路设计有限公司 Temperature coefficient correction method in SOC (system on a chip) and SOC (system on a chip)
US9306402B1 (en) * 2013-02-07 2016-04-05 Analog Devices, Inc. Circuits and methods for capacitor charging
JP2016103772A (en) * 2014-11-28 2016-06-02 株式会社大真空 Oscillator
US10256771B2 (en) 2016-06-10 2019-04-09 Fujitsu Limited Crystal oscillator device and method of measuring crystal oscillator characteristic
US10333480B2 (en) 2016-06-10 2019-06-25 Fujitsu Limited Crystal oscillator device and method of measuring crystal oscillator characteristic
US10340850B2 (en) 2016-06-10 2019-07-02 Fujitsu Limited Crystal oscillator device and method of measuring crystal oscillator characteristic
US10355641B2 (en) 2016-06-10 2019-07-16 Fujitsu Limited Crystal oscillator device and method of measuring crystal oscillator characteristic
US10355640B2 (en) 2016-06-10 2019-07-16 Fujitsu Limited Crystal oscillator device and method of measuring crystal oscillator characteristic
US10476435B2 (en) 2016-06-10 2019-11-12 Fujitsu Limited Crystal oscillator, crystal resonator controlling method, and crystal resonator controlling device

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KR960016733B1 (en) 1996-12-20
EP0601515A1 (en) 1994-06-15
AU5219593A (en) 1994-06-16
JPH06177645A (en) 1994-06-24
AU671316B2 (en) 1996-08-22
CA2110756A1 (en) 1994-06-08
CA2110756C (en) 1998-02-03
DE69326742D1 (en) 1999-11-18
JP2626432B2 (en) 1997-07-02
DE69326742T2 (en) 2000-04-06
EP0601515B1 (en) 1999-10-13
KR940015958A (en) 1994-07-22

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